In recent years, in the process of becoming larger in size and higher in definition of a liquid crystal display panel, suppression of pattern misalignment of a pixel array due to heat treatment during a production process is one of the most important problems. A metal wiring of a semiconductor element array formed on a substrate becomes narrower by the demand of high definition, and as a result, the tolerance of pattern misalignment is getting smaller.
It is considered that pattern misalignment is caused by a thermal shrinkage due to structural relaxation of a glass substrate in a production process of a liquid crystal display panel. A first method proposed to suppress the thermal shrinkage is to decrease an average coefficient of thermal expansion of a glass. As glasses using this method are proposed a non-alkali glass having an average coefficient of thermal expansion at from 30° C. to 380° C. of from 25×10−7/° C. to 36×10−7/° C. (Patent Document 1) and a non-alkali glass having an average coefficient of thermal expansion at from 50° C. to 300° C. of from 30×10−7/° C. to 43×10−7/° C. (Patent Document 2). Furthermore, a glass having an average coefficient of thermal expansion close to that of a-Si, p-Si or the like film-formed on the glass substrate is also proposed (Patent Document 3).
A second method is to increase a strain point of a glass. Patent Document 1 proposes to increase a strain point to 640° C. or higher, Patent Document 2 proposes to increase a strain point to 710° C. or higher and lower than 725° C., and Patent Document 3 proposes to increase a strain point to 680° C. or higher and lower than 740° C.
In addition, to suppress deflection of a glass, it is proposed to decrease a density of a glass (Patent Documents 1, 2) or to increase Young's modulus (Patent Document 3).